Synthesis and characterization of microstructures of MgO/Au composite films grown by reactive RF magnetron sputtering

The MgO/Au composite thin films were synthesized by reactive RF magnetron sputtering on n-type Si(100) substrate. The influence of the growth conditions on the microstructures of the MgO/Au films was evaluated. The MgO/Au films were characterized with X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy. The results show that the growth conditions, particularly the substrate temperature, ratio of Ar/O₂ gas flow rates, and sputtering modes(co-sputtering and step-by-step sputtering), have a major impact on the MgO/Au film growth. For example, co-sputtering mode resulted in formation of Au grains on the MgO/Au surfaces because of Au fast deposition rate, but step-by-step sputtering mode reduced the Au content to a mole ratio of 7.30%. Besides, high substrate temperature promoted MgO grain growth. Deposited in a step-by-step sputtering mode at a substrate temperature of 500℃ and a ratio of Ar/O₂ gas flow rate of 5.0, the MgO grains with a size about 30~40 nm formed. Depending on the ratio of Ar/O₂ flow rate, three preferred growth orientations: (111), (200), and (220), were observed.